Kinetic Properties and Enantioselectivity of The Lipases Produced by Four Aspergillus Species

Four high lipase-producing Aspergillus species, selected in our laboratory, were compared in terms of their stability and reactivity for enantioselective esterification between (R, S)-2-octanol with octanoic acid in n-hexane. We determined the pH and temperature reactions dependences of lipases activities, and we found that these enzymes exhibited various pH sensitivities. The optimum pH observed for Aspergillus terreus lipase was 5.5, for A. niger and A. oryzae lipases in the range of 6.0 to 6.5 and pH 7.0 for A. flavus lipase. Good stability was observed at pH ranging from 5.0 to 8.5 after 24 hours at 40° C, and the optimum activity was observed at 35–40° C for all lipases tested. The lipases from A. terreus and A. niger were highly thermostable, retaining 60% and 50% activity at 60° C after 1 hour, respectively. The lipases from A. niger and A. terreus lipases provided the best results in terms of enantioselectivity (E) in the esterification of (R, S)-2-octanol with octanoic acid in n-hexane (E = 4.9 and E = 4.5, respectively). These properties make these lipases good candidates for biocatalysis in organic media.     

Reduction of raffinose oligosaccharides in chickpea (Cicer arietinum) flour by crude extracellular fungal α-galactosidase

The efficiency of crude extracelluar α-galactosidases from Cladosporium cladosporides, Aspergillus oryzae and A niger in reducing the raffinose and stachyose content in chickpea flours was studied and compared with other traditional treatments. The optimum pH for α-galactosidase activity was found to be 4·5 for A oryzae and 5·0 for Cl cladosporides and A niger, while the optimum temperature of enzyme activity was 40°C for Cl cladosporides and 50°C for A oryzae and A niger. The specific activities of α-galactosidase from Cl cladosporides, A oryzae and A niger were 3·35, 3·94 and 5·94 units μg⁻¹ protein, respectively. The enzyme activity was stable between pH 4·0 and 7·0 for A oryzae and A niger and between pH 5·0 and 7·0 for Cl cladosporides. The enzymes were thermostable when incubated at temperature ranges of 40–60°C for Cl cladosporides and 40–50°C for A oryzae and A niger. The optimum conditions for removing the raffinose and stachyose were obtained by incubating chickpea flours with 30 ml of crude fungal α-galactosidase extract (290, 210 and 130 units ml⁻¹ for Cl cladosporides, A oryzae and A niger, respectively) for 3 h at the optimum conditions of each strain. Crude fungal α-galactosidases reduced the raffinose oligosaccharides content in chickpea flours by 100%, while germination reduced the raffinose content by 69% and stachyose content by 75%. Other traditional techniques reduced the raffinose content by 13–49% and stachyose content by 10–32%. © 1998 Society of Chemical Industry     

Hot air-assisted radio frequency heating effects on wheat and corn seeds: Quality change and fungi inhibition

Hot air-assisted radio frequency (RF) heating has been proposed and studied as an alternative disinfestation method for grain seeds. In this study, hot air-assisted RF heating effects on fungi inhibition and its influence on physiological (seed vigor, germination rate) and biochemical (color, enzyme activity) qualities of wheat and corn seeds were further investigated. Results showed that high intensity hot air-assisted RF treatment (70 °C, 10 min) reduced seed vigor and germination rate for both wheat and corn seeds, but relatively mild intensity treatment (65 °C, 10 min) showed no significant influence on color and germination rate, and even enhanced enzyme activity (Superoxide dismutase-SOD, catalase-CAT and peroxidase-POD). Moreover, hot air-assisted RF treatment (65 °C, 10 min) reduced Aspergillus flavus by 2 and 3 log-scale (CUF/g) in wheat and corn seeds with the moisture content of 12.0%, and 3 and 4 log-scale for wheat and corn seeds when moisture content increased to 15.0%, respectively. These results indicated higher moisture content (a_w) of grain seeds would benefit fungi inhibition for hot air-assisted RF treatment, and with proper control of treatment conditions, hot air-assisted RF heating has the potential to inhibit fungi and maintain physiological and biochemical quality of grain seeds.     

High Temperature Storage Effect on Longevity of Rice Seeds

Storage of Indica (Oryza sativa L. cv. Katakutara) and Japonica (Oryza sativa L. cv. Kusabue) rice seeds at 30° and 40°C for 2 months in the dark did not result in the loss of viability in both cultivars. Storage at 60°C, however, resulted in a complete loss of germination after 45 days in the case of Kusabue while the Katakutara rice seeds retained the germination potential well above 95%. Corresponding increases in the linoleic acid content of the free fatty acid fraction and TBA values of the extracted lipid fraction were also observed in Kusabue rice seeds. The investigation indicated that the Indica rice seeds were better protected than the Japonica rice seeds by the enclosing rice hull during the storage period.     

Germination, Growth, and Toxin Production of Nonproteolytic Clostridium botulinum as Affected by Multiple Barriers

ABSTRACT The effect of combinations of pH (6.5, 5.75), NaCl (0.25,1.75%), and incubation temperatures (7,13 °C) on spore germination, outgrowth, and time to toxicity of nonproteolytic Clostridium botulinum was examined in a broth system. Spores of four toxin type E and nonproteolytic type B were inoculated (10⁴/ml) into Tryptone Peptone Glucose Yeast Extract (TPGY) broth. Cultures were monitored for three weeks, or until toxin was detected. A modified FSIS‐amplified ELISA (comparable in sensitivity to the mouse bioassay) was used to screen cultures for neurotoxin. Combinations of the most inhibitory level for each barrier reduced the degree and rate of germination, the lag and growth rate of vegetative cells, and the time to toxicity.     

Inactivation of Bacillus cereus Spores on Red Chili Peppers Using a Combined Treatment of Aqueous Chlorine Dioxide and Hot‐Air Drying

The effect of a combined treatment using aqueous chlorine dioxide (ClO₂) and hot‐air drying to inactivate Bacillus cereus spores on red chili peppers was evaluated. Ten washed and dried pepper samples, each comprising half of a single pepper (Capsicum annuum L.), were inoculated with B. cereus spore suspension. The inoculated samples were washed with sodium hypochlorite (NaOCl; 50, 100, or 200 μg/mL) or ClO₂ (50, 100, or 200 μg/mL) solution for 1 min and then air‐dried (25 ± 1 °C, 47 ± 1% relative humidity), which was followed by drying with hot air at 55 °C for up to 48 h. The spore populations on the samples were enumerated and their a_w and chromaticity values were measured. The spore numbers immediately after treatment with NaOCl and ClO₂ were not significantly different. A more rapid reduction in spore numbers was observed in the samples treated with ClO₂ than those treated with NaOCl during drying. A combined treatment of ClO₂ and hot‐air drying significantly reduced the spore populations to below the detection limit (1.7 log CFU/sample). B. cereus spores on chili peppers were successfully inactivated by washing with ClO₂ solution followed by hot‐air drying whereas the pepper color was maintained.     

Effect of Germination,under Different Environmental Conditions,on Saponins,Phytic Acid and Tannins in Lentils (Lens culinaris)

The effect of germination conditions on some antinutrients of Lens culinaris var Magda 20 seeds were studied. The seeds were germinated at 20°C under variable conditions of time, water and light. Quantitative analyses of the soyasapogenols, inositol phosphates and tannins were carried out by capillary gas chromatography, high-performance liquid chromatography and spectrophotometric techniques respectively. Germinated seeds at day 6 contained higher levels soyasapogenol B than the controls, whereas in general the tannin content was reduced. Total phytic acid amounts did not decrease after 3 days of germination but was greatly reduced after 6 days. This work shows that the optimal conditions to reduce some antinutritional factors (tannins and phytic acid) in lentils were 6 days of seed germination in dark and with alternate watering. Therefore, germination conditions offer a good opportunity to improve the nutritional quality of lentils. © 1997 SCI.     

Effect of Rooibos (Aspalathus linearis) on Growth Control of Clostridium perfringens and Lipid Oxidation of Ready‐to‐Eat Jokbal (Pig's Trotters)

This study investigated the antimicrobial effects of rooibos (tea extract), potassium lactate (PL) and sodium diacetate (SDA) mixture alone or in combinations on the growth of Clostridium perfringens vegetative cell and spore in ready‐to‐eat (RTE) Jokbal (pig's trotters). Addition of a combination of 10% rooibos and 4% PL + SDA inhibit growth of C. perfringens vegetative cell in Jokbal at 24 °C and 36 °C. The significant inhibition on germination and growth of C. perfringens spores was also observed in Jokbal with a combination of 10% rooibos and 4% PL + SDA (PL: 2.24%, SDA: 0.16%) at 24 °C. The Jokbal treated with 10% rooibos and 4% PL + SDA mixture had significantly (P < 0.05) lower TBARS values than the control at 10 and 24 °C. The lipid oxidation inhibition effect was the highest (P < 0.05) in anaerobic packed Jokbal with 10% rooibos. The addition of a combination of 10% rooibos and 4% PL + SDA during the processing of Jokbal prevented the growth of C. perfringens and the germination and growth of C. perfringens spores at room temperature. This study shows rooibos tea as a valuable natural food preservative in meat products.     

Effects of Germination on Proteins, Raffinose Oligosaccharides, and Antinutritional Factors in the Great Northern Beans (Phaseolus vulgaris L.)

During 5 day germination, the major reserve proteins of the Great Northern bean (Phaseolus vulgaris L.) were substantially hydrolyzed. In vitro trypsin digestion of the extracted proteins up to 4 hr at 37°C indicated that the major storage proteins in germinated and the ungerminated seeds, although substantially hydrolyzed, could not be completely degraded. In vitro susceptibility of the extracted proteins was improved on moist heat treatment (97°C, 30 min). A substantial increase in soluble essential amino acids occurred during germination. Highest decrease in stachyose + raffimose (76.40%) was observed at the end of the third day of germination. Trypsin, chymotrypsin, and α-amylase inhibitory activities and phytic acid were reduced respectively by 62.9, 73.4, 67.1, and 57.8% after 5 days of germination.     

Influence of water activity and temperature on conidial germination and mycelial growth of ochratoxigenic isolates of Aspergillus ochraceus on grape juice synthetic medium. Predictive models

The first stages in the development of Aspergillus ochraceus, an ochratoxin A‐producing fungus that infects grapes and may grow on them, have been studied on a synthetic nutrient medium similar to grape in composition. Spore germination and mycelial growth have been tested over a water activity (a_w) and temperature range which could approximate to the real conditions of fungal development on grapes. Optimal germination and growth were observed at 30 °C for all three isolates tested. Maximal germination rates were detected at 0.96–0.99 a_w at 20 °C, while at 10 and 30 °C the germination rates were significantly higher at 0.99 a_w. Although this abiotic factor (a_w) had no significant influence on mycelial growth, growth rates obtained at 0.98 a_w were slight higher than those at other a_w levels. Predictive models for the lag phase before spore germination as a function of water activity and temperature have been obtained by polynomial multiple linear regression, and the resulting response surface models have been plotted. Copyright © 2005 Society of Chemical Industry     

Effect of biopolymers containing natamycin against Aspergillus niger and Penicillium roquefortii on fresh kashar cheese

Fungal spoilage during refrigerated storage is one of the main safety and quality‐related problems for dairy products. The effect of wheat gluten (WG) and methyl cellulose (MC) biopolymers containing natamycin (NA) on the growth of Aspergillus niger and Penicillium roquefortii on the surface of fresh kashar cheese during storage at 10 °C for 30 days was investigated. Wrapping of A. niger‐inoculated cheese with MC films containing 5–20 mg NA per 10 g resulted in approximately 2‐log reductions in spore count. Two mg NA per 10 g included into WG films was sufficient to eliminate A. niger on the surface of cheese. However, MC and WG films containing NA did not cause any significant decrease in P. roquefortii count on the cheese surface. Therefore, especially use WG films in dairy applications could be an effective way of controlling A. niger growth on these products.     

STUDIES ON THE EFFECT OF GERMINATION TIME AND TEMPERATURE ON MALTING OF RICE

The effect of germination conditions on rice malt quality was studied by germinating rice for different periods of time up to 7 days over a range of temperatures (22° to 32°C). Germination time and temperature had a significant effect on rice malt diastatic power, cold and hot water extracts, total reducing sugars, and free alpha amino nitrogen. In general, diastatic power, cold water extract, hot water extract, total reducing sugars and free alpha amino nitrogen, all increased with germination time and temperature. Germination temperatures of 28°C and 30°C were good for the development of diastatic power, cold water extract, hot water extract, total reducing sugars and free alpha amino nitrogen. However germinating at 30°C gave maximum result. The mashing trials with rice malted for 6 days showed a slow and incomplete saccharification, slow filtration rate, and high total available extract in spent grains.     

Effect of seed treatments on the chemical composition of two amaranth species: oil,sugars, fibres,minerals and vitamins

The effects of seed treatments, including cooking, popping, germination and flour air classification on several components of Amaranthus caudatus and A. cruentus seeds, including oil, sugars, fibre, minerals and vitamins were studied. The lipid, crude and dietary fibre, ash, and sugar contents were 71, 43, 140, 30 and 18 g kg^?1 in raw A. caudatus and 85, 39, 134, 40 and 22 g kg^?1 in raw A. cruentus seeds, respectively. Sucrose was the dominant sugar in the raw and thermal treated seeds of both species, while glucose and galactose were the dominant ones in the high protein and the germinated seed flours. Phosphorus, potassium, magnesium and calcium were the dominant minerals in the raw seeds of both species. Air classification increased the content of minerals by more than 35% while thermal treatments did not affect their content and germination increased the calcium and zinc contents. The ascorbic acid contents were 0.030 and 0.023 g kg^?1 sample in raw A. caudatus and A. cruentus seeds, respectively. All the treatments reduced the ascorbic acid content, with a high effect for the air classification and the germinated seeds dried at 90 °C. The levels of vitamin B complex, including niacin, niacinamide, pyridoxine and riboflavin were increased in the high protein flour fraction (protein contents of these fractions of A. caudatus and A. cruentus were 263.9 g kg^?1 and 246.6 g kg^?1, respectively) and decreased in the thermal treated flours. Germination mostly increased the amounts of those vitamins while drying reduced their amounts. Copyright © 2005 Society of Chemical Industry     

Preliminary studies of the germination behaviour of guinea corn (Sorghum vulgare)

Sorghum seeds (Sorghum vulgare, variety Sorghum bicolor L181) were germinated in the dark for 12, 18, 24, 36, 48, 54, 60 and 66 h respectively. Optimum moisture content for germination was between 35 and 40%. Active germination and growth were assessed in terms of soluble carbohydrate and total starch in the seedling. Germination occurred between 15 and 30°C with an optimum at 22°C.     

Inhibition of Clostridium perfringens Spore Germination and Outgrowth by Lemon Juice and Vinegar Product in Reduced NaCl Roast Beef

Abstract: Inhibition of Clostridium perfringens spore germination and outgrowth in reduced sodium roast beef by a blend of buffered lemon juice concentrate and vinegar (MoStatin LV1) during abusive exponential cooling was evaluated. Roast beef containing salt (NaCl; 1%, 1.5%, or 2%, w/w), blend of sodium pyro‐ and poly‐phosphates (0.3%), and MoStatin LV1 (0%, 2%, or 2.5%) was inoculated with a 3‐strain C. perfringens spore cocktail to achieve final spore population of 2.5 to 3.0 log CFU/g. The inoculated products were heat treated and cooled exponentially from 54.4 to 4.4 °C within 6.5, 9, 12, 15, 18, or 21 h. Cooling of roast beef (2.0% NaCl) within 6.5 and 9 h resulted in <1.0 log CFU/g increase in C. perfringens spore germination and outgrowth, whereas reducing the salt concentration to 1.5% and 1.0% resulted in >1.0 log CFU/g increase for cooling times longer than 9 h (1.1 and 2.2 log CFU/g, respectively). Incorporation of MoStatin LV1 into the roast beef formulation minimized the C. perfringens spore germination and outgrowth to <1.0 log CFU/g, regardless of the salt concentration and the cooling time. Practical Application: Cooked, ready‐to‐eat meat products should be cooled rapidly to reduce the risk of Clostridium perfringens spore germination and outgrowth. Meat processors are reducing the sodium chloride content of the processed meats as a consequence of the dietary recommendations. Sodium chloride reduces the risk of C. perfringens spore germination and outgrowth in meat products. Antimicrobials that contribute minimally to the sodium content of the product should be incorporated into processed meats to assure food safety. Buffered lemon juice and vinegar can be incorporated into meat product formulations to reduce the risk of C. perfringens spore germination and outgrowth during abusive cooling.     

Processing of yellow pea by germination,microwave treatment and drying

A high content of α-galactooligosaccharides affects the nutritive value of legumes. In agreement with papers concerning the effect of germination on the composition of various grain legumes, our results show that the most important decrease of α-galactooligosaccharides (raffinose family oligosaccharides — RFO) in the yellow pea (Pisum sativum) occurs during the first 3 days of germination. Wet germinated peas were treated by microwave (MW) energy and dried by hot air at 80°C. The benefit of MW treatment is shortening and improvement of drying. Proposed processing steps for the modification of nutritional properties of pea include: (1) germination of pea seeds (3 days); (2) MW treatment of germinated seeds; (3) drying by hot air; (4) grinding of dried seeds; and (5) preparation of meal from the modified pea flour.     

Starch Characterisation of Araucaria angustifolia and Araucaria araucana Seeds

Araucaria angustifolia and Araucaria araucana are conifers that cover different areas of South America. Their seeds have been consumed from prehistoric times until today in Brazil, Argentina and Chile. In this work, the starch of Araucaria angustifolia and Araucaria araucana seeds were analysed by light and environmental scanning electron microscopy, X‐ray diffraction, and differential scanning calorimetry. The starch granules of A. angustifolia and A. araucana were round or slightly oval, with a central hilum. Both starches gave X‐ray diffraction patterns compatible with the A‐type, with strong peaks at 15°, 17°, and 23°. The gelatinisation temperature of A. angustifolia starch (68.5°C) was higher than that of A. araucana (66.6°C), probably due to the higher amylose content of the former (22.4 % and 17.3 %, respectively). The thermograms of A. araucana starch presented a minor peak at about 71°C, which was attributed to the fact that the starch granules population of A. araucana was heterogeneous, with large and small granules, whereas A. angustifolia starch contained mainly large granules.     

Seed treatments affect functional and antinutritional properties of amaranth flours

The effects of seed treatments, including cooking, popping germination and flour air classification, on the functional properties and antinutritional factors of Amaranthus caudatus and Amaranthus cruentus seeds were studied. Thermal treatments increased the water absorption with a maximum value of 5.1 and 6.3 g g⁻¹ in flour of popped seeds of both species. Generally, fat absorption increased after the treatments. Air classification and germination followed by drying at low temperature increased the foam stability of the flours, while thermal treatment and germination followed by drying at higher temperatures reduced the foam stability. All treatments except air classification decreased the emulsion stability. Also, all treatments except germination followed by drying at 30 °C increased the flour dispersibility, whereas the soluble nitrogen index was increased in the germinated seed flours and decreased in thermal treated seeds and air‐classified flours. Air classification increased the contents of phenolic compounds and phytate and decreased the contents of enzyme inhibitors, whereas the thermal treatments reduced the contents of phenolic compounds, phytate and enzyme inhibitors to a greater extent for cooking than for popping. Germination followed by drying reduced the level of phenolic compounds, phytate and enzyme inhibitors. Copyright © 2006 Society of Chemical Industry     

Effect of seed treatments on the chemical composition and properties of two amaranth species: starch and protein

The seeds of two Amaranth species were studied. The starch contents were 543 and 623 g kg^?1 while crude protein contents were 154 and 169 g kg^?1 for Amaranthus caudatus and Amaranthus cruentus seeds, respectively. The effect of several treatments, including cooking, popping and germination and flour air classification on the protein and starch properties were studied. Air classification decreased the starch content and increased the protein content, while heating increased the protein but did not affect the starch content. Germination decreased both starch and protein contents. Amylose content was increased by air classification and heating, but was not affected by germination. It was found that all treatments increased the starch swelling power and reduced the falling number. The resistant starch content was increased in the high protein flour (HPF) fraction and germinated flour compared with the raw flour, while its content decreased in the heat treated seed flours. These processes also affected the starch gelatinization temperature and peak viscosity. The thermal properties of the starch flour were not affected by air classification while gelatinization energy was decreased significantly (by 52.0 and 90.0% and by 70.0 and 95.0%) in cooked and popped A caudatus and A cruentus seed flours, respectively. The gelatinization energy was highest in germinated seeds dried at 90 °C with values of 2.67 and 3.87 J g^?1. Air classification reduced the level of all protein fractions. Thermal treatment decreased the water‐soluble fraction (albumins + globulins) and alcohol‐soluble fraction (prolamins) in both species. The levels of all fractions except the water‐soluble fraction (albumins + globulins) were reduced significantly in both species by germination, which mainly increased the amount of aspartic acid, serine and alanine, while the amounts of threonine, arginine and tyrosine decreased in both species. The polypeptide bands of the HPF in both species were unchanged compared with the raw seed flours, but more intensive coloured bands were observed. Thermal treatments eliminated major and minor bands above 35.0 KDa in both species. Copyright © 2004 Society of Chemical Industry     

Effects of Germination and Osmopriming Treatment on Enhancement of Isoflavone Contents in Various Soybean Cultivars and Cheonggukjang (Fermented Unsalted Soybean Paste)

ABSTRACT: To develop soybean products containing high isoflavone contents, the effects of germination and osmopriming on the isoflavone contents of 3 soybean cultivars (Ilmi, Daehwang, and Taekwang) were investigated. Total isoflavone contents of Ilmi and Daehwang cultivars were not significantly different with soaking time at 20 and 25 °C. Ilmi and Taekwang cultivars had higher total isoflavone contents at 0.243 to 0.256 and 0.072 to 0.079 g/100 g, respectively, after 12 h of germination at 20 °C than those at 0.232 and 0.064 g/100 g at the initial stage. After 48 h of germination at 20 °C, contents of total isoflavone, daidzein, and genistein were 0.246, 0.094, and 0.147 g/100 g, respectively. In contrast, after 48 h of germination and 0.2 M NaCl treatment at 20 °C, those contents increased up to 0.346, 0.140, and 0.203 g/100 g, respectively. Total isoflavone and genistein contents of cheonggukjang prepared with germinated soybean or soybeans treated with osmopriming were 0.322 and 0.198 g/100 g, 0.332 and 0.201 g/100 g, respectively, at 48 h of fermentation, and were higher than those of the control group (0.277 and 0.169 g/100 g). We concluded that cheonggukjang would contain higher isoflavone contents after the treatment of germination and osmopriming.